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研发客服硬件信息：FL2440板子，s3c2440CPU带四个LED，分别在链接GPB5，GPB6，GPB8，GPB10
内核版本：linux-3.8.0
led驱动代码如下：
值得注意地方地方：
1，定时器的使用：在include/linux/timer.h下定义struct timer_list
struct timer_list {
/*
* All fields that change during normal runtime grouped to the
* same cacheline
*/
struct list_head entry;
unsigned long expires;
struct tvec_base *base;
void (*function)(unsigned long);
unsigned long data;
int slack;
#ifdef CONFIG_TIMER_STATS
int start_pid;
void *start_site;
char start_comm[16];
#endif
#ifdef CONFIG_LOCKDEP
struct lockdep_map lockdep_map;
#endif
};
详细参考：linux-2.4.18内核定时器的使用
2，设置GPIO函数有中，linux-3.8.0和linux-3.0.0有所不同，具体可以参考Documentation/arm/Samsung-S3C24XX/GPIO.txt中的说明,只列出遇到变换：
| linux-3.8.0 | linux-3.0.0 | 参数是否变化 | |
| 设置GPIO高或低 | gpio_set_value（） | s3c2410_gpio_setpin() | 不变 |
| 设置GPIO工作方式 | s3c_gpio_cfgpin() | s3c2410_gpio_cfgpin() | 不变 |
3，Linux核心几个重要跟时间有关的名词或变数，HZ、tick和jiffies之间关系。
HZ：Linux核心每隔固定周期会发出timer interrupt ，HZ是用来定义每一秒有几次timer interrupts，我的机器为100 timer interrupts。
tick:就是HZ的倒数，以秒表示
jiffies：Jiffies为Linux核心变数(32位元变数，unsigned long)，它被用来纪录系统自开机以来的tick数，每发生一次timer interrupt，Jiffies变数会被加一。
4，设备节点自动创建函数：class_create()和device_create（）
从linux 内核2.6.24的某个版本之后，devfs不复存在，udev成为devfs的替代。udev处于应用层;加入对udev的支持很简单，以一个字符设备驱动led为例，在驱动初始化的代码里调用class_create为该设备创建一个class，再为每个设备调用 device_create创建对应的设备。
大致用法如下：
struct class *class = class_create(THIS_MODULE, “led”);
device_create(class, NULL, MKDEV(major_num, 0), NULL, “led”);
这样的module被加载时，udev daemon就会自动在/dev下创建led设备文件。
led驱动代码plat_led.c：
/*********************************************************************************
* Copyright: (C) 2011 Guo Wenxue
* All rights reserved.
*
* Filename: s3c_led.c
* Description: This is the common LED driver runs on S3C24XX.
*
* Version: 1.0.0(10/27/2011~)
* Author: Guo Wenxue
* ChangeLog: 1, Release initial version on "10/27/2011 11:39:10 AM"
*
********************************************************************************/
#include "s3c_driver.h"
#define DRV_AUTHOR "Guo Wenxue
#define DRV_DESC "S3C24XX LED driver"
/* Driver version*/
#define DRV_MAJOR_VER 1
#define DRV_MINOR_VER 0
#define DRV_REVER_VER 0
#define DEV_NAME DEV_LED_NAME
//#define DEV_MAJOR DEV_LED_MAJOR
#ifndef DEV_MAJOR
#define DEV_MAJOR 0 /* dynamic major by default */
#define TIMER_TIMEOUT 40
static int debug = DISABLE;
static int dev_major = DEV_MAJOR;
static int dev_minor = 0;
/* ============================ Platform Device part ===============================*/
/* LED hardware informtation structure*/
struct s3c_led_info
{
unsigned char num; /* The LED number */
unsigned int gpio; /* Which GPIO the LED used */
unsigned char active_level; /* The GPIO pin level(HIGHLEVEL or LOWLEVEL) to turn on or off */
unsigned char status; /* Current LED status: OFF/ON */
unsigned char blink; /* Blink or not */
};
/* The LED platform device private data structure */
struct s3c_led_platform_data
{
struct s3c_led_info *leds;
int nleds;
};
/* LED hardware informtation data*/
static struct s3c_led_info s3c_leds[] = {
[0] = {
.num = 1,
.gpio = S3C2410_GPB(5),
.active_level = LOWLEVEL,
.status = ON,
.blink = DISABLE,
},
[1] = {
.num = 2,
.gpio = S3C2410_GPB(6),
.active_level = LOWLEVEL,
.status = OFF,
.blink = DISABLE,
},
[2] = {
.num = 3,
.gpio = S3C2410_GPB(8),
.active_level = LOWLEVEL,
.status = OFF,
.blink = DISABLE,
},
[3] = {
.num = 4,
.gpio = S3C2410_GPB(10),
.active_level = LOWLEVEL,
.status = OFF,
.blink = DISABLE,
},
};
/* The LED platform device private data */
static struct s3c_led_platform_data s3c_led_data = {
.leds = s3c_leds,
.nleds = ARRAY_SIZE(s3c_leds),
};
struct led_device
{
struct s3c_led_platform_data *data;
struct cdev cdev;
struct class *dev_class;
struct timer_list blink_timer;
} led_device;
static void platform_led_release(struct device * dev)
{
int i;
struct s3c_led_platform_data *pdata = dev->platform_data;
dbg_print("%s():%dn", __FUNCTION__,__LINE__);
/* Turn all LED off */
for(i=0; i
{
/* for linux-3.8.0 */
gpio_set_value(pdata->leds[i].gpio, ~pdata->leds[i].active_level);
#if 0
/* for linux-3.0.0 check in s3c2410_gpio_setpin() in Documentation/arm/Samsung-S3C24XX/GPIO.txt*/
s3c2410_gpio_setpin(pdata->leds[i].gpio, ~pdata->leds[i].active_level);
#endif
}
}
static struct platform_device s3c_led_device = {
.name = "s3c_led",
.id = 1,
.dev =
{
.platform_data = &s3c_led_data,
.release = platform_led_release,
},
};
/* ===================== led device driver part ===========================*/
void led_timer_handler(unsigned long data)
{
int i;
struct s3c_led_platform_data *pdata = (struct s3c_led_platform_data *)data;
for(i=0; i
{
if(ON == pdata->leds[i].status)
{
gpio_set_value(pdata->leds[i].gpio, pdata->leds[i].active_level);
}
else
{
gpio_set_value(pdata->leds[i].gpio, ~pdata->leds[i].active_level);
}
if(ENABLE == pdata->leds[i].blink ) /* LED should blink */
{
/* Switch status between 0 and 1 to turn LED ON or off */
pdata->leds[i].status = pdata->leds[i].status ^ 0x01;
}
/* time clock */
mod_timer(&(led_device.blink_timer), jiffies + TIMER_TIMEOUT);
}
}
static int led_open(struct inode *inode, struct file *file)
{
struct led_device *pdev ;
struct s3c_led_platform_data *pdata;
pdev = container_of(inode->i_cdev, struct led_device, cdev);
pdata = pdev->data;
file->private_data = pdata;
return 0;
}
static int led_release(struct inode *inode, struct file *file)
{
return 0;
}
static void print_led_help(void)
{
printk("Follow is the ioctl() command for LED driver:n");
printk("Enable Driver debug command: %un", SET_DRV_DEBUG);
printk("Get Driver verion command : %un", GET_DRV_VER);
printk("Turn LED on command : %un", LED_ON);
printk("Turn LED off command : %un", LED_OFF);
printk("Turn LED blink command : %un", LED_BLINK);
}
/* compatible with kernel version >=2.6.38*/
static long led_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
struct s3c_led_platform_data *pdata = file->private_data;
switch (cmd)
{
case SET_DRV_DEBUG:
dbg_print("%s driver debug now.n", DISABLE == arg ? "Disable" : "Enable");
debug = (0==arg) ? DISABLE : ENABLE;
break;
case GET_DRV_VER:
print_version(DRV_VERSION);
return DRV_VERSION;
case LED_OFF:
if(pdata->nleds <= arg)
{
printk("LED%ld doesn't existn", arg);
return -ENOTTY;
}
pdata->leds[arg].status = OFF;
pdata->leds[arg].blink = DISABLE;
break;
case LED_ON:
if(pdata->nleds <= arg)
{
printk("LED%ld doesn't existn", arg);
return -ENOTTY;
}
pdata->leds[arg].status = ON;
pdata->leds[arg].blink = DISABLE;
break;
case LED_BLINK:
if(pdata->nleds <= arg)
{
printk("LED%ld doesn't existn", arg);
return -ENOTTY;
}
pdata->leds[arg].blink = ENABLE;
pdata->leds[arg].status = ON;
break;
default:
dbg_print("%s driver don't support ioctl command=%dn", DEV_NAME, cmd);
print_led_help();
return -EINVAL;
}
return 0;
}
static struct file_operations led_fops = {
.owner = THIS_MODULE,
.open = led_open,
.release = led_release,
.unlocked_ioctl = led_ioctl, /* compatible with kernel version >=2.6.38*/
};
static int s3c_led_probe(struct platform_device *dev)
{
struct s3c_led_platform_data *pdata = dev->dev.platform_data;
int result = 0;
int i;
dev_t devno;
/* Initialize the LED status */
for(i=0; i
{
s3c_gpio_cfgpin(pdata->leds[i].gpio, S3C2410_GPIO_OUTPUT);